Highly cut-resistant yarn and protective articles made therefrom

ABSTRACT

A cut-resistant composite yarn, comprising a high strength organic fiber having a tenacity greater than 15 grams per denier and a hard-particle-filled thermoplastic fiber useful in making fabrics from which protective articles, such as gloves are made.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to cut-resistant fibers and yarns andparticularly their use in gloves and other protective apparel.

2. Description of Related Art

Improved resistance to cutting with a sharp edge has long been sought.Cut-resistant gloves are beneficially utilized in the meatpackingindustry and in automotive applications. As indicated by U.S. Pat. Nos.4,004,295, 4,384,449, and 4,470,251, and by EP 458,343, gloves providingcut resistance have been made from yarn which includes flexible metalwire or which consist of highly oriented fibers having high modulus andhigh tensile strength, such as aramids, thermotropic liquid crystallinepolymers, and extended chain polyethylene. A drawback to gloves madefrom yarn that includes flexible metal wire is hand fatigue withresultant decreased productivity and increased likelihood of injury.Moreover, with extended wear and flexing, the wire may fatigue andbreak, causing cuts and abrasions to the hands. In addition, the wirewill act as a heat sink when a laundered glove is dried at elevatedtemperatures, which may reduce tensile strength of the yarn or fiber,thereby decreasing glove protection and glove life.

Improved flexibility and comfort and uncomplicated laundering aredesirable in cut-resistant, protective apparel. Therefore, there is aneed for a flexible, cut-resistant fiber that retains its propertieswhen routinely laundered. Such a fiber may be advantageously used inmaking protective apparel, in particular highly flexible, cut-resistantgloves.

Polymers have been mixed with particulate matter and made into fibers,but not in a way that significantly improves the cut resistance of thefiber. For example, small amounts of particulate titanium dioxide havebeen used in polyester fiber as a delustrant. Also used in polyesterfiber is a small amount of colloidal silicon dioxide, which is used toimprove gloss. Magnetic materials have been incorporated into fibers toyield magnetic fibers. Examples include: cobalt/rare earth elementintermetallics in thermoplastic fibers, as in published Japanese PatentApplication No. 55/098909 (1980); cobalt/rare earth elementintermetallics or strontium ferrite in core-sheath fibers, described inpublished Japanese Patent Application No. 3-130413 (1991); and magneticmaterials in thermoplastic polymers, described in Polish Patent No.251,452 and also in K. Turek et al., J. Magn. Magn. Mater. (1990), 83(1-3), pp. 279-280. Also, U.S. Pat. No. 5,597,649 is directed to a yarn,which is a composite of a high modulus fiber and a particle-filledfiber, wherein the high modulus fiber can be an aramid fiber.

Various kinds of gloves have been made in which metal has been includedin the fabrication of the glove to impart protective qualities to theglove. For example, U.S. Pat. Nos. 2,328,105 and 3,185,751 teach that aflexible, X-ray shield glove may be made by treating sheets of asuitable porous material with a finely divided, heavy metal which may belead, barium, bismuth or tungsten, or may be made from a latex ordispersion containing heavy metal particles. As illustrated by U.S. Pat.No. 5,020,161, gloves providing protection against corrosive liquidshave been made with a metal film layer. These gloves also do not appearto have significantly improved cut resistance.

SUMMARY OF THE INVENTION

In one embodiment, this invention is a cut-resistant composite yarn,comprising a high strength organic fiber having a tenacity greater than15 grams per denier and a hard-particle-filled thermoplastic fiberuseful for making cut-resistant fabrics that can be made into protectivearticles, such as gloves, aprons, chaps, sleeves, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 a and 1 b are schematic sketches of the chamber used in theTorture Chamber Test.

FIG. 2 is a sketch of a test glove as used in the Torture Chamber Test.

DETAILED DESCRIPTION OF THE INVENTION

The invention is a highly cut resistant yarn and articles for personalprotective use such as gloves, aprons, chaps, and the like and theprocess for manufacturing them. The articles are made from yarns thatare a combination of a high strength organic fiber and a thermoplasticcarrier fiber filled with hard particles.

Within the embodiment of this invention the term “high strength organicfiber” is understood to mean a fiber with a tenacity greater than 15grams per denier that is formed by any of the polymerization reactionscommonly known in the art from monomers based on a carbon backbone.Preferably, high strength organic fibers do not include carbon fiber.Typical high strength organic fibers embodied by this invention includebut are not limited to fibers with a tenacity greater than 15 grams perdenier formed from para-aramid, polybenzazole, polybenzoxazole,polybenzothiazole, polybenzimidazole, polyacrylate, and copolymersthereof.

In one embodiment of this invention, the carrier fiber is formed from anisotropic semi-crystalline polymer. Typical fibers are fibers formedfrom polymers such as poly(alkylene terephthalate), poly(alkylenenaphthalate), poly(arylene sulfide), aliphatic, and aliphatic-aromaticpolyamide, and polyesters made from monomer units derived fromcyclohexanedimethanol and terephthalic acid. In another embodiment ofthis invention, the carrier fiber is formed from a liquid crystallinepolymer (LCP) that is preferably thermotropic. Typical LCP fibers areformed from polymers such as aromatic polyester, aliphatic-aromaticpolyester, aromatic poly(estercarbonate), aliphatic-aromaticpoly(esteramide), aromatic poly(esterimide), aromatic poly(esteramide),aromatic polyamide, aliphatic-aromatic polyamide, and poly(azomethine).

The hard particles used to fill the thermoplastic fibers of thisinvention may be characterized as having a MOHS hardness value ofgreater than 5. Preferably, the average particle size distribution ofthe hard particles will be in the range of 1 to 6 microns. Typicalmaterials that may comprise the hard particles include but are notlimited to tungsten, copper, brass, bronze, aluminum, steel, iron,monel, cobalt, titanium, magnesium, silver, molybdenum, tin, zinc,aluminum oxide, tungsten carbide, metal nitrides, metal sulfates, metalphosphates, metal borides, silicon dioxide, silicon carbide, baddelyte,chloritoid, clinozoiste, chondrodite, euclasite, petalite, sapphire,spodumene, staurolite, clay, or alumina.

In one embodiment of this invention, the hard particle filledthermoplastic fiber is a thermoplastic fiber in which the hard particlefiller is essentially uniformly distributed. The hard particle filler ispresent in the amount of 0.1 to 10 (optionally 0.1 to 5) weight percentbased on the total weight of the particle filled fiber.

In another embodiment of this invention, the hard particle filledthermoplastic fiber is the core fiber of a sheath/core fiber in whichthe hard particle filler is essentially uniformly distributed within thecore material of the sheath/core fiber. Preferably, the hard particlefiller is present in the amount of 0.1 to 10 (optionally 0.1 to 5)weight percent based on the total weight of the sheath/core fiber.

The articles are preferably made by knitting from yarns that arecomprised of a combination of poly(paraphenylene terephthalamide) fibersold by E.I. du Pont de Nemours and Company (DuPont), Wilmington, Del.under the trade name KEVLAR® and polyester CRF (cut resistant fibers).The polyester CRF is preferably an alumina-filled (about 10%)multifilament yarn as generally described in U.S. Pat. No. 5,851,668.The polyester is preferably poly(ethylene terephthalate). The polyestercut resistant fibers are available from Honeywell under the trademarkBarricut®. The inventive yarns comprise about 32 to 65% of cut resistantpolyester fiber; however, as the percentage cut resistant polyesterincreases beyond about 65%, the performance in cut protection decreases.The cut-resistant fabric that is a combination of KEVLAR® and polyesterhas cut resistance as measured by ASTM F1790-97 greater than that of acomparable weight fabric made entirely of either fiber. Additionally,unlike an article made wholly of polyester cut-resistant fabric, anarticle made of the inventive fabric is very resistant to cutting inshearing operations, such as with scissors.

Further, such articles in the form of gloves demonstrate exceptionallylong life in the torture chamber test (TCT). The inventive glovesdemonstrated dramatically better performance than gloves made eitherwholly of KEVLAR® or wholly of polyester CRF. Dupont developed the TCT(described in detail below) to evaluate the performance of cut resistantmaterial in extreme conditions, where standard cut protectionperformance tests do not accurately predict performance in real-lifesituations.

The ply-twisted yarns of this invention are made by twisting together atleast two individual single yarns. It is well known in the art to twistsingle yarns together to make ply-twisted yarns. Each single yarn canbe, for example, a collection of staple fibers spun into what is knownin the art as a spun staple yarn.

By the phrase “twisting together at least two individual single yarns”,it is meant the two single yarns are twisted together without one yarnfully covering the other. This distinguishes ply-twisted yarns fromcovered or wrapped yarns where a first single yarn is completely wrappedaround a second single yarn so that the surface of the resultingply-twisted yarn only exposes the first single yarn.

The ply-twisted yarns of this invention are preferably made up of atleast two different single yarns. The ply-twisted yarns also preferablyhave a total linear density of from 300 to 2000 dtex. The individualfibers in a single yarn typically have a linear density of 0.5 to 7dtex, with the preferred range being 1.5 to 3 dtex. The ply-twistedyarns, and the single yarns that make up those ply-twisted yarns, caninclude other materials as long as the function or performance of theyarn or fabric made from that yarn is not compromised for the desireduse.

Test Methods

The cut protection performance test (CPPT) was performed in accordancewith ASTM F1790-97.

Tabor Abrasion Resistance was measured in accordance with ASTM D3389.

The scissor cut resistance test was performed by cutting the articlewith a pair of 8-inch carbon steel scissors of the type commonly usedfor household or office applications and subjectively evaluating therelative ease/difficulty encountered in cutting.

The torture chamber test is conducted in a 16-inch diameter Lucitecylinder 10 closed at both ends, which is depicted schematically inFIGS. 1 a and 1 b. Six (6) blade holders 12 are mounted on the inside ofthe cylinder around the periphery at 60 degree intervals (cylinderinside diameter is 14.5 inches). Each blade holder accepts 4 single edgerazor blades 14 angled front-to-back in the cylinder at 45 degrees. RedDevil single edge industrial razor blades are used. The cylinder isrotated around its central axis, driven by an electric motor, not shown.The rotational speed of the cylinder was 35 revolutions per minute. Therespective materials were tested in the form of gloves. Each glove wasfilled with 400 gm of nylon pellets and the glove was closed at thewrist to contain the pellets and then was placed alone in the TortureChamber. The test glove is depicted schematically in FIG. 2. New razorblades were used for each glove evaluation. Time to failure was definedas the time when nylon pellets were first observed in the TortureChamber. The test is discontinued if no pellets are observed within 180minutes. Immediately upon observing any beads, rotation of the TortureChamber was stopped and the glove was removed and examined for visualconfirmation of a cut. This was to ensure that the glove had actuallyfailed and that the pellets had not been released because the tied-offwrist area had loosened.

EXAMPLES

The materials were evaluated by knitting the various fibers into fabricsamples or into gloves as required for the specific tests.

Example 1 and Comparative Examples A and B

Knitted fabric samples at 12.5 oz/yd² basis weight were made as follows:Comparative Example A 100% polyester CRF Comparative Example B 100%KEVLAR

Example 1

52% KEVLAR/48% CRF, wherein the KEVLAR and CRF were combined to produceco-twisted (plied) yarns. Two of the co-twisted yarns were then co-fedinto the knitting machine to produce the fabrics.

The results of CPPT and Tabor Abrasion testing are provided in Table 1.TABLE 1 Example CPPT Tabor Abrasion Resistance A 1125 gms 325 cycles B 775 gms 360 cycles 1 1255 gms 430 cycles

Example 2 - 3 and Comparative Examples C and D

Knitted fabric and gloves at 19 oz/yd² basis weight were made asfollows: Comparative Example C 100% polyester CRF Comparative Example D100% KEVLAR

Example 2

68% KEVLAR/32% polyester CRF, wherein knitting was done utilizing threefeed yarns, whereby two of the yarns were as described in Example 1 andthe third feed yarn was 100% KEVLAR.

Example 3

35% KEVLAR/65% polyester CRF, wherein knitting was done utilizing threefeed yarns, whereby two of the yarns were as described in Example 1 andthe third feed yarn was 100% polyester CRF

The following test results provided in Table 2 are from fabrics, exceptfor the torture chamber tests, which were performed on gloves made fromthe respective fabrics. TABLE 2 Torture Chamber Scissor Example CPPTTabor Abrasion Life Ressistance C 1525 gms 790 cycles 0.2 minutes  easyD 1185 gms 440 cycles 15 minutes difficult 2 1750 gms 120 minutes difficult 3 2259 gms 90 minutes Not tested

1. A cut-resistant composite yarn, comprising a high strength organicfiber having a tenacity greater than 15 grams per denier and ahard-particle-filled thermoplastic fiber.
 2. The yarn of claim 1,wherein the thermoplastic fiber is a liquid crystalline polymer selectedfrom the group consisting of aromatic polyester, aliphatic-aromaticpolyester, aromatic poly(estercarbonate), aliphatic-aromaticpoly(esteramide), aromatic poly(esterimide), aromatic poly(esteramide),aromatic polyamide, aliphatic-aromatic polyamide and poly(azomethine).3. The yarn of claim 1, wherein the thermoplastic fiber is asemi-crystalline polymer selected from the group consisting ofpoly(alkylene terephthalate), poly(alkylene naphthalate), poly(arylenesulfide), aliphatic polyamide, aliphatic-aromatic polyamide andpolyesters made from monomer units derived from cyclohexanedimethanoland terephthalic acid.
 4. The yarn of claim 3, wherein the thermoplasticfiber is poly(ethylene terephthalate).
 5. The yarn of claim 3,comprising 32 to 65 weight percent poly(ethylene terephthalate) based onthe weight of the yarn.
 6. The yarn of claim 1 wherein the high strengthorganic fiber is selected from the group consisting of para-aramids,polybenzazoles, polybenzoxazoles, polybenzothiazoles,polybenzimidazoles, polyacrylates and copolymers thereof.
 7. The yarn ofclaim 5, wherein the high strength organic fiber is para-aramid.
 8. Theyarn of claim 6, wherein the para-aramid is poly(paraphenyleneterephthalamide).
 9. The yarn of claim 1, wherein the hard particles areselected from the group consisting of tungsten, copper, brass, bronze,aluminum, steel, iron, monel, cobalt, titanium, magnesium, silver,molybdenum, tin, zinc, aluminum oxide, tungsten carbide, metal nitrides,metal sulfates, metal phosphates, metal borides, silicon carbide,baddelyte, chloritoid, clinozoiste, chondrodite, euclasite, petalite,sapphire, spodumene, staurolite and clay.
 10. The yarn of claim 8,wherein the hard particles comprise aluminum oxide.
 11. The yarn ofclaim 1, wherein the average particle size distribution of the hardparticles is between 1 and 6 micrometers.
 12. The yarn of claim 8,wherein the hard particles are present in the amount of 0.1 to 10 weightpercent based on the total weight of the hard-particle-filledthermoplastic fiber.
 13. The yarn of claim 11, wherein the thermoplasticfiber has a sheath-core configuration and the hard particles aresubstantially contained within the core.
 14. A cut resistant fabric,comprising the cut-resistant yarn of claim
 1. 15. A cut resistantfabric, comprising a cut-resistant composite yarn, wherein the yarncomprises poly(paraphenylene terephthalamide) and poly(ethyleneterephthalate) filled with about 0.1 to 10 weight percent of hardparticles, based on the total weight of hard particles pluspoly(ethylene terephthalate).
 16. The cut resistant fabric of claim 13,wherein the fabric is woven.
 17. The cut resistant fabric of claim 13,wherein the fabric is knit.
 18. The fabric of claim 13, wherein thefabric has a cut protection performance value of at least 500 grams at abasis weight of at least 6 ounces per square yard when tested inaccordance with ASTM F1790-97.
 19. The fabric of claim 13, wherein thefabric has a cut protection performance value of at least 1000 grams ata basis weight of at least 12 ounces per square yard when tested inaccordance with ASTM F1790-97.
 20. The fabric of claim 13, wherein thefabric has a cut protection performance value of at least 1500 grams ata basis weight of at least 19 ounces per square yard when tested inaccordance with ASTM F1790-97.
 21. The fabric of claim 13, wherein thecut protection performance when tested in accordance with ASTM F1790-97is greater than the cut protection performance of a fabric of equalbasis weight and construction consisting of any single yarn of which thecomposite yarn of claim 1 comprises.
 22. A protective article,comprising the fabric of claim 13, wherein the protective article isselected from the group consisting of aprons, chaps, sleeves and gloves.23. The article of claim 21, wherein the fabric is woven.
 24. Thearticle of claim 21, wherein the fabric is knit.
 25. A glove inaccordance with claim 21, wherein the torture chamber life of the gloveexceeds the torture chamber life of a glove of equal basis weightconsisting of only one fiber of the yarn.
 26. The glove of claim 23,having a torture chamber life of at least 90 minutes when the basisweight of the fabric is at least 19 oz/yd².
 27. A glove made form thefabric of claim 14, having a torture chamber life of at least 90 minuteswhen the basis weight of the fabric is at least 19 oz/yd².